Electrical switch



Jan. 30, 1940. P. N. ROSEBY ELECTRICAL SWITCH Filed Nov. 7, 1935 2 Sheets-Sheet 1 Arrr Jan. 30, 1940. P. N. ROSEBY 2,188,519

ELECTRICAL swITcH Filed Nov. '7, 1935 2 Sheets-Sheet 2 K mf W1 '15 1e INSULATION S Patented Jan. 30, 1940 UNITED STATES PATENT OFFICE ELECTRICAL SWITCH Application November I, 1935, Serial No. 48,611 In Great Britain December 21, 1934 5 Claims.

The present invention relates to electrical signalling systems and is more particularly concerned with systems for effecting remotely-controlled operations by means of high frequency 5 currents superimposed on electric supply mains.

Such an arrangement may find advantageous application for the control of street lighting and for the operation of tariff changeover equipment or special circuits on domestic consumers premises.

10 The chief objects of the invention are to enable two classes of equipment for instance water heaters and street lights to be separately controlled and also to enable a centrally-controlled switching operation to be cancelled automatically l5 locally.

According to one feature of the invention a suitable selective control is obtained by arranging that all the switching units for one class of equipment are tuned to operate from a characteristic frequency only, whereas the switching units' which control the other class of equipment are responsive to a wide band of frequencies, but are in addition equipped with a delay device which prevents their functioning from the pulses which 25 control the first class which are of very short duration.

A further feature of the invention is the arrangement whereby switching units which switch off for instance in response to a control pulse 30 automatically switch on again a predetermined time after the reception of the control pulse which causes them to switch off. This is particularly advantageous for water heaters and is conveniently achieved by the use of a timing device .':3 comprising an eddy-current motor and gearing such as used in watt-hour meters of the usual type, which is set in operation when the water heater is switched off so that after a predetermined lapse of time, which can be readily adl justed. it advances to a position in which the heater is again connected in circuit.

The invention will be better understood from the following description of one method of carrying it into effect, reference being had to the accompanying drawings comprising Figs. 1-3. Fig. 1 shows schematically the main elements of a three-phase power distribution system having a water heater switching unit and a street light switching unit connected between the neutral 5n conductor and earth, while Figs. 2 and 3 show actual constructions and details of a water heater switching unit.

Although only two units are shown in Fig. 1 it will be understood that it is the intention that a 55 large number shall be connected in parallel to the neutral conductor, the load circuits being distributed among the phases as found desirable.

The system is supplied by way of the main transformer having a high-voltage delta-connected primary P and a low voltage star-con- 5 nected secondary S. The phase conductors are represented by 1, 2 and 3, and the neutral conductor N is connected to earth at the substation by way of the low resistance secondary of the signalling transformer T.

Frequency generators HFGI and HFG2 of for instance the type described in the application of Philip N. Roseby, Serial No. 4646, filed February 2, 1935 are used to produce pulses of control frequency for transmission over the neutral con- 8 ductor to operate the switching units. Preferably the lighting units will be operated from pulses of 5000 cycles having a duration of say half a second, while the heating units will be operated from pulses of 500 cycles having a duration of say thirty seconds. The heater units which are not tuned will energise from the 5000 cycle lighting control pulses but as will appear such energisation is not of sufilcient duration to produce effective operation. This arrangement avoids the expense of a. filter in each heating unit.

Considering the operation of the circuit, when a 500 cycle pulse is applied to the neutral conductor from the high frequency generator HFGI each of the control relays A in the water heater units operates to energise a bi-metallic strip B which is attached to a pivoted arm F and carries a friction pad M at its free end. After the required delay period, the strip bends away from the drum G thus freeing itself and permitting the associated arm F to fall by gravity on to a stop.

As a result of this movement the extension J which has previously been holding contact spring K against its right hand contact I will allow the spring K to move over to the left-hand contact H where it is held by means of the permanent magnet L acting on a pole piece secured to the spring.

The circuit to the water heater WH which extends over contact I is now interrupted while at 46 contact H the circuit is completed for the eddycurrent motor C which commences to drive the drum G in a clockwise direction through suitable reduction gearing as shown. Meanwhile, owing to the cessation of the signalling pulse the cir- 50 cult of the thermostat is opened and it cools of! thereby restoring the friction pad M at its free end into engagement with the rotating drum G. The thermostat and pivoted arm F now rotate with the drum and after a suitable period of time has elapsed, for example an hour, the extension J will move the contact spring K ever on to contact I so that the water heater WH is again connected in circuit, while at the same time the circuit to the eddy-current motor is opened at the contact H.

During peak load conditions therefore, a single pulse of 500 cycle current over the neutral con- U include the usual thermostat-operated switch controlled by the temperature of the water and also a switch for cutting the water heater out of service.

The feature of automatically switching on has important advantages both from the consumers point of view and from that of the supply authorities since it ensures that even if the heaters are switched off accidentally either from the power station or as the result of extraneous interference they will automatically be restored after the lapse of the predetermined period of time.

The street lighting units such as SL are operated from pulses of 5000 cycles of half a second duration applied by the high frequency generator HFG2 and are each provided with a filter circuit FC arranged to cut oif below 5000 cycles so as to prevent their operation from the water heater pulses. In this case the switching is done by means of an electromagnetic step-by-step switching device which may be of the type illustrated in the application of Cecil R. Woodland, Serial No. 758,573, filed December 21, 1934.

Figures 2 and 3 show the actual mechanical details of a heater unit following the principle of that shown in Fig. 1, and employing a positively-engaging clutch instead of a friction arrangement.

Fig. 2 is a front elevation of the device, while Fig. 3 is a side view from which the majority of the co-operating parts can be appreciated.

The various elements are supported on a main frame I secured to a suitable backboard and provided with a front cover plate 2. The coils 8 are arranged with suitable pole pieces so that when they are connected to the mains, which occurs when the load equipment is switched off, they eifect the rotation of the eddy current disc l. The disc 4 by means of the worm gears 8 and 6 drives a gear wheel I which meshes with a larger gear wheel 8. Rotatable on the same shaft as the gear wheel 8 is the U-shaped member 8 which is secured to one end of the spiral spring 10; the other end of which is anchored to the frame. At its opposite end the member 8 carries the bellcrank lever H which is pivoted thereto at It. One end of this lever is adapted to engage in the teeth of the gear wheel 8, while the other end co-operates with the thermostat l8 which is fixed to the front plate 2. It will be appreciated that the function of the end of the lever which engages with the teeth of the gear wheel 8 is the same as that performed by the friction pad M in Fig. 1. A reciprocatory member carrying an arm II and a contact spring I 4 is pivoted about points 22 and 22'. The member 8 when moved to its extreme position against the action of the spring I8 is arranged to engage the arm 2| and operate the contact spring I thereby moving it out of engagement with contact I! and into engagement with contact l6. At contact I! the circuit for the coils 8 is broken while at contact IS the main load is connected up. The motor is arranged to have a slight overrun so as to secure a reliable operation of the contact spring I and this is further ensured by the provision of a permanent magnet ll cooperating with the reciprocatory member so as to secure reliable contact in the pomtion in which the spring I is not operated by the member 9.

The operation of the device will be followed from what has already been said but may be briefly described as follows: In the normal position the member 8 will have been advanced by the engagement of bell-crank lever H with gear wheel 8 to the position in which the spring I0 is fully wound, and the contact I! is operated into engagement with the fixed contact 18. This closes the circuit for the water heater or other device which may of course also be controlled by its own thermostat or by a switch operated by the user. When a 500-cycle signal is sent out from the control point, current is supplied to the thermostat I3 which gradually heats up and bends to the left. When this movement has proceeded sufliciently far, the member II is tilted about the pivot I 2 and its other end is moved out of engagement with the teeth of the gear wheel 8. Accordingly the member 9 restores to normal against the rubber-covered stop 18 under the action of the spring I 0 and the contact spring l4 now leaves contact l6 and engages contact l5. This has the effect of closing the motor circuit and starting the rotation of the gear wheel 8. At the end of the signal the thermostat l3 quickly cools oflf thereby permitting the member H to engage once more in the teeth of the gear wheel 8. These conditions are maintained until the member 8 has been carried round sufficiently far to operate member I4 again whereupon the motor circuit is opened and the water heater is again switched on. a

It will be appreciated that in certain circumstances a further signal may be sent before member 9 has again operated contact I4 and in this case the timing period will be restarted from the beginning since the thermostat I8 is able to operate the member I I in any position and thus restore member 9 to its starting position. The flag l9 seen in Fig. 2 is fixed to the same shaft as gear wheel 1 and by its movement affords the maintenance man a convenient indication of whether the motor is running.

In case automatic restoration of the water heating units is not required, the eddy-current motor and the equipment it drivescould be dispensed with an in these circumstances it would be arranged for the thermostat to control a stepby-step electromagnetic switching device substantially identical with those used for the lighting control or any other type of switch adapted to take up one of two positions.

The arrangement for automatic restoration of the water heating circuits could of course be employed independently of any provision for street lighting or other separate switching. Moreover the invention is not limited to control over the neutral conductor since the phase leads could be used for achieving the same results and in certain circumstances their use might be preferable to the use of the neutral conductor.

I claim:

1. In a circuit controlling device, a circuit controlling switch, a switch operating member for moving said switch from one position to another position, a driving member, means for linking said members together to cause movement oi said driving member to be communicated to said operating member to thereby operate said switch, a control circuit, a thermal element for controlling said linking means and efiective to cause said members to be disengaged responsive to current flow of predetermined duration in said control circuit, whereby said operating member is eflective to restore said switch to said one position when said members are disengaged.

2. In a circuit controlling device, a circuit controlling switch, an operating member for moving said switch from one position to another position, a driving member, a motor actuating said driving member, a circuit for said motor completed over said switch when same occupies said one position, means for linking said members together to cause movement of said driving member to be communicated to said operating member to thereby operate said switch to said other position, said switch eflective when operated to said other position to interrupt said motor circuit to halt said driving member, a control circuit, athermal element for controlling said linking means and effective to cause said members to be disengaged responsive to current flow of predetermined duration in said control circuit, and means for moving said operating member to permit said switch to restore to said one position when the members are disengaged to cause actuation 01' said driving member to be resumed.

3. In a circuit controlling device, a circuit controlling switch, a switch operating member, a driving member, means for linking said members together to cause movement of the driving member to be communicated to said operating member to thereby operate said switch from one position to another position, a control circuit, means responsive to current flow of a certain duration in said control circuit for controlling said linking means to disengage said members and then, an interval of time after the cessation of said current flow, to automatically re-engage said members, and means for moving said operating member to permit said switch to restore to said one position responsive to said disengagement of said members, said driving member moving said operating member to reoperate said switch to said other position a predetermined interval of time after said reengagement.

4. In a circuit controlling device such as claimed in claim 3, a motor for actuating said driving member, and a circuit for said motor controlled by said switch to cause the driving member to be actuated only when the switch occupies said one position.

5. In a circuit controlling device, a normally restored circuit controlling switch, a reciprocatory switch-operating member mounted for movement between a normal and an extreme position and eflective to operate said switch only when occupying said extreme position, a driving member, means for linking said members together to cause movement of said driving member to be communicated to said operating member to move said operating member slowly toward said extreme position thereby to operate said switch after a predetermined interval of time, a control circuit, means responsive to current flow of a certain duration in said control circuit for controlling said linking means to disengage said members and to automatically re-engage them after a predetermined delay, means for restoring said operating member to its normal position during said disengagement, whereby operation of said switch may be delayed longer than said predetermined interval 01' time by causing said members to be so disengaged as often as desired during the time said operating member is being moved toward said extreme position.

PHILIP NORTON ROSEBY. 

